U.S. patent application number 14/184807 was filed with the patent office on 2014-10-23 for check valve device in the suction side of a hydrostatic power-unit that can be operated in the same direction of rotation as a pump and as a motor.
This patent application is currently assigned to Linde Hydraulics GmbH & Co. KG. The applicant listed for this patent is Linde Hydraulics GmbH & Co. KG. Invention is credited to Lukas Krittian, Alfred Langen.
Application Number | 20140314587 14/184807 |
Document ID | / |
Family ID | 50028841 |
Filed Date | 2014-10-23 |
United States Patent
Application |
20140314587 |
Kind Code |
A1 |
Krittian; Lukas ; et
al. |
October 23, 2014 |
Check Valve Device In The Suction Side of A Hydrostatic Power-Unit
That Can Be Operated In The Same Direction of Rotation As A Pump
And As A Motor
Abstract
A hydrostatic power-unit (7) is connected with an internal
combustion engine (2). The suction side (S) of the power-unit (7),
when operating as a pump, sucks hydraulic fluid from a tank (9) and
delivers into a delivery side (P), and when operating as a motor is
driven by hydraulic fluid from a hydraulic accumulator (20). A
check valve device (30) is located in the suction side (S) to
provide a pressure increase when the power-unit (7) is operated as
a motor. The check valve device (30) has a check valve (32)
operated by an actuator device (31). The actuator device (31)
actuates the check valve (32) between a closed position (32a) in
which a connection of the suction side (S) with the tank (9) is
shut off, and an open position (32b) in which the connection of the
suction side (S) to the tank (9) is opened.
Inventors: |
Krittian; Lukas;
(Aschaffenburg, DE) ; Langen; Alfred;
(Aschaffenburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Linde Hydraulics GmbH & Co. KG |
Aschaffenburg |
|
DE |
|
|
Assignee: |
Linde Hydraulics GmbH & Co.
KG
Aschaffenburg
DE
|
Family ID: |
50028841 |
Appl. No.: |
14/184807 |
Filed: |
February 20, 2014 |
Current U.S.
Class: |
417/364 ;
137/511 |
Current CPC
Class: |
Y02T 10/6208 20130101;
F02B 73/00 20130101; Y02T 10/62 20130101; F02N 7/00 20130101; B60K
2006/126 20130101; B60K 6/12 20130101; Y10T 137/7837 20150401; B60W
10/06 20130101; B60W 30/18018 20130101 |
Class at
Publication: |
417/364 ;
137/511 |
International
Class: |
F02B 73/00 20060101
F02B073/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2013 |
DE |
102013101796.7 |
Feb 26, 2013 |
DE |
102013101868.8 |
Claims
1. A check valve device for a hydrostatic power-unit in a drive
connection with an internal combustion engine, comprising: a check
valve device located in a suction side of a hydrostatic power-unit
operable as a pump and a motor such that when the power-unit is
operated as a motor, a pressure increase is provided on the suction
side, wherein the check valve device includes a check valve
connected to an actuator device, and wherein the actuator device
actuates the check valve between a closed position in which a
connection of the suction side with a tank in the direction of flow
from the suction side to the tank is shut off, and an open position
in which the connection of the suction side to the tank is
opened.
2. The check valve device as recited in claim 1, wherein the check
valve is actuated by the actuator device into the open position
when the power-unit is operated as a pump and into the closed
position when the power-unit is operated as a motor.
3. The check valve device as recited in claim 1, wherein the check
valve is actuated by a spring device into the closed position and
the check valve is actuated into the open position by a hydraulic
actuation pressure applied to the actuator device.
4. The check valve device as recited in claim 1, wherein in the
closed position the check valve is pressurized in the closed
position by hydraulic pressure from a hydraulic accumulator
connected to the suction side.
5. The check valve device as recited in claim 1, wherein the
actuator device comprises a positioning piston connected with the
check valve.
6. The check valve device as recited in claim 5, wherein the
positioning piston is operatively connected to a spring device and
includes a piston pressure chamber pressurized with an actuation
pressure that counteracts the spring device.
7. The check valve device as recited in claim 6, wherein the spring
device is located in a spring-side piston pressure chamber of the
positioning piston connected with the tank.
8. The check valve device as recited in claim 1, wherein the
actuator device comprises a control pressure surface located on the
check valve and pressurizable by a hydraulic actuation pressure
that actuates the check valve in the direction of the open
position.
9. The check valve device as recited in claim 1, wherein the check
valve comprises a flapper valve with a pivotable flapper in an
operative connection with the actuator device.
10. The check valve device as recited in claim 9, wherein the
positioning piston is connected with the flapper by a tie rod
connected in an articulated manner to the flapper and in an
articulated manner to the positioning piston.
11. The check valve device as recited in claim 9, wherein the
pivotable flapper is located in a suction channel, and when in the
open position the flapper does not protrude into the suction
channel.
12. The check valve device as recited in claim 1, wherein the check
valve comprises a flat slide valve with a longitudinally
displaceable slide operatively connected with the actuator
device.
13. The check valve device as recited in claim 1, wherein the check
valve comprises a piston slide valve with a longitudinally
displaceable or rotatable piston operatively connected with the
actuator device.
14. A hydrostatic power-unit, comprising: a hydrostatic power-unit
in a drive connection with an internal combustion engine, wherein
the hydrostatic power-unit is operable as a pump and as a motor,
wherein in pump operation the power-unit sucks hydraulic fluid via
a suction side from a tank and delivers into a delivery side, and
wherein in motor operation the power-unit is driven by hydraulic
fluid under pressure from a hydraulic accumulator and fed via the
suction side; and a check valve device located in the suction side
of the hydrostatic power-unit, wherein the check valve device
includes a check valve connected to an actuator device, and wherein
the actuator device actuates the check valve between a closed
position in which a connection of the suction side with the tank in
the direction of flow from the suction side to the tank is shut
off, and an open position in which the connection of the suction
side to the tank is opened.
15. The hydrostatic power-unit as recited in claim 14, wherein the
check valve device includes an independent housing.
16. The hydrostatic power-unit as recited in claim 15, wherein the
housing of the check valve device is flange-mounted on a housing of
the power-unit.
17. The hydrostatic power-unit as recited in claim 20, including a
control valve that controls a connection of the hydraulic
accumulator with the suction side of the power-unit for operation
as a motor.
18. The hydrostatic power-unit as recited in claim 14, wherein the
power-unit is a variable displacement power-unit with a variable
displacement volume, wherein the displacement volume is set by a
displacement volume control device actuated by a control device,
and wherein the control device is connected to a charging pressure
circuit and with the hydraulic accumulator for a supply of
hydraulic fluid.
19. The hydrostatic power-unit as recited in claim 18, including a
shut-off valve that shuts off flow in a direction of the charging
pressure circuit and is located in a connection line between the
control device and the charging pressure circuit.
20. The hydrostatic power-unit as recited in claim 18, wherein the
hydraulic accumulator is in communication with the suction side of
the power-unit by a connecting line in which the control valve is
located, and wherein to supply the control device with hydraulic
fluid from the hydraulic accumulator, a hydraulic line is provided
which is connected to the connecting line between the control valve
and the suction side of the power-unit.
21. The hydrostatic power-unit as recited in claim 20, wherein the
hydraulic line is connected to a control pressure line that runs
from the charging pressure circuit to the control device, wherein
the shutoff valve is located in the control pressure line, and
wherein the hydraulic line is connected to the control pressure
line between the shutoff valve and the control device.
22. The hydrostatic power-unit as recited in claim 20, including a
pressure reducer valve located in the hydraulic line.
23. The hydrostatic power-unit as recited in claim 14, wherein the
charge pressure of a charging pressure circuit is the actuation
pressure of the actuator device of the check valve.
24. The hydrostatic power-unit as recited in claim 22, including a
branch line from the hydraulic line to the actuator device, wherein
a shutoff valve that shuts off the flow to the pressure reducer
valve is located between the pressure reducer valve and the
connection of the branch line.
25. The hydrostatic power-unit as recited in claim 23, wherein the
actuator device comprises a positioning piston and a piston
pressure chamber of the positioning piston is in communication with
the charging pressure circuit and a spring-side piston compression
chamber of the positioning piston is depressurized to the tank.
26. The hydrostatic power-unit as recited in claim 14, wherein the
check valve includes a control pressure surface and the control
pressure surface of the check valve is connected with a charging
pressure circuit and an additional control pressure surface is
provided on the check valve which actuates the check valve toward
the closed position, and wherein the additional control pressure
surface for pressurization is connected with the suction side
between the power-unit and the check valve.
27. The hydrostatic power-unit as recited in claim 14, including a
switching valve for control of the pressurization of the actuator
device, by means of which, in a first switched position, the check
valve is actuated into the open position as a function of the
actuation pressure and by means of which, in a second switched
position, the check valve is actuated into the closed position.
28. The hydrostatic power-unit as recited in claim 27, wherein, in
the first switched position of the switching valve, a piston
pressure chamber of a positioning piston is pressurized with the
actuation pressure and a spring-side piston pressure chamber is
depressurized to the tank, and in the second switched position of
the switching valve, the spring-side piston pressure chamber of the
positioning piston is pressurized with the actuation pressure and
the piston pressure chamber is depressurized to the tank.
29. The hydrostatic power-unit as recited in claim 27, wherein, in
the first switched position of the switching valve, a control
pressure surface of the check valve is pressurized with the
actuation pressure and an additional control pressure surface of
the check valve is connected with the suction side between the
power-unit and the check valve.
30. The hydrostatic power-unit as recited in claim 29, wherein, in
the second switched position of the switching valve, the control
pressure surface and the additional control pressure surface of the
check valve are pressurized with the actuation pressure.
31. The hydrostatic power-unit as recited in claim 29, wherein in
the second switched position of the switching valve, the control
pressure surface is depressurized to the tank and the additional
control pressure surface is pressurized with the actuation
pressure.
32. The hydrostatic power-unit as recited in claim 27, wherein in
the closed position of the check valve, a connection of the suction
side with the tank is provided in the direction of flow from the
tank to the suction side.
33. The hydrostatic power-unit as recited in claim 17, wherein the
control valve and/or the switching valve is/are actuated
electrically and is/are in an operative connection with an
electronic control device.
34. The hydrostatic power-unit as recited in claim 33, wherein the
electronic control device is in communication with a sensor device
which measures a speed of rotation of the internal combustion
engine and/or a sensor device that measures the pressure of the
hydraulic accumulator.
35. The hydrostatic power-unit as recited in claim 14, wherein the
hydrostatic power-unit is operable in the same direction of
rotation as a pump and as a motor, wherein in pump operation the
power-unit supplies at least one user, and wherein in motor
operation the power-unit is a hydraulic starter for a start-stop
function of the internal combustion engine and/or is a hydraulic
booster drive when the internal combustion engine is running.
36. The hydrostatic power-unit as recited in claim 35, wherein for
a start-stop function of the internal combustion engine, when the
internal combustion engine is shut off, the check valve is actuated
by the spring device into the closed position, and after startup of
the internal combustion engine by operating the hydrostatic
power-unit as a motor, the check valve is actuated into the open
position by the hydraulic actuation pressure present at the
actuator device generated when the internal combustion engine is
running.
37. The hydrostatic power-unit as recited in claim 35, wherein for
the booster drive when the internal combustion engine is running,
the check valve is actuated into the closed position by the
hydraulic actuation pressure for the duration of the operation of
the booster drive.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to German Application Nos.
DE 102013101796.7 filed Feb. 22, 2013 and DE 102013101868.8 filed
Feb. 26, 2013, both of which are herein incorporated by reference
in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a check valve device of a
hydrostatic power-unit that is in a drive connection with an
internal combustion engine and can be operated as a pump and as a
motor. The power-unit, when operating as a pump, sucks hydraulic
fluid from a tank on a suction side and delivers into a delivery
side and, when operated as a motor, is driven by hydraulic fluid
under pressure taken from a hydraulic accumulator and fed via the
suction side. The check valve device is located in the suction side
of the hydrostatic power-unit to achieve an increase in pressure on
the suction side when the power-unit is operated as a motor.
[0004] 2. Description of Related Art
[0005] Self-propelled mobile machines, in particular industrial
trucks, agricultural equipment, forestry equipment, and
construction equipment, such as excavators, wheeled and telescoping
loaders, tractors, combine harvesters, forage harvesters, and sugar
beet and potato diggers, have a drivetrain with an internal
combustion engine that drives a traction drive and also the working
hydraulics that perform the work functions of the machine. At least
one hydraulic pump driven by the internal combustion engine is
provided to supply the working hydraulics with hydraulic fluid.
[0006] During idle operation, when the traction drive and the
working hydraulics are not actuated and no torque is required from
the internal combustion engine, the internal combustion engine is
operated at a lower idle speed. Idle operation of this type occurs
during pauses or interruptions in the work.
[0007] To reduce the fuel consumption of the internal combustion
engine during pauses or interruptions in work, a start-stop
function can be provided for the internal combustion engine in
which the internal combustion engine, operating at no load, is shut
off during pauses or interruptions in work and is automatically
restarted when there is a demand for torque from a work function or
from the traction drive. The shutoff and subsequent restarting of
the internal combustion engine can occur even after relatively
brief idle times, so that the starting process of the internal
combustion engine is an operation that must be carried out
relatively frequently and at brief intervals during the operation
of the internal combustion engine. This requirement places severe
demands on the starter device of the internal combustion engine
with regard to fatigue strength and the ability to deliver the
starting energy required to start the internal combustion
engine.
[0008] In mobile machines, hydrostatic power-units are used as
hydraulic starters of the internal combustion engine for the
start-stop function and are in a drive connection with the
crankshaft of the internal combustion engine. During startup of the
internal combustion engine, these hydraulic starters are operated
with hydraulic fluid from a hydraulic accumulator, which
accumulator is charged before the shutoff of the internal
combustion engine. DE 10 2011 105 006 A1 describes a drivetrain in
which, in addition to the hydraulic pump of the working hydraulics,
an additional hydraulic motor is provided that functions as a
starter of the internal combustion engine to provide the start-stop
function. Because the additional hydraulic motor is in coupled
motion during the normal operation of the running internal
combustion engine, losses occur that reduce the overall efficiency
of the machine. The presence of an additional hydraulic motor as
the starter of the internal combustion engine also requires
additional construction cost and effort and occupies additional
space.
[0009] To eliminate the cost and effort required for an additional
hydraulic motor as a starter for the internal combustion engine on
mobile machines with a start-stop function, the hydraulic pump that
is already present for the working hydraulics can be used as the
hydraulic starter of the internal combustion engine by operating
the hydraulic pump in the same direction of rotation and same
direction of flow of the hydraulic fluid as a motor by supplying
hydraulic fluid from a hydraulic accumulator to the suction side
which is connected to a tank. As a general rule, the hydraulic pump
of the working hydraulics is operated in an open circuit and is in
communication on a suction side with a suction connection for a
hydraulic fluid tank, and delivers the hydraulic fluid into a
delivery line connected to a delivery connection. When operated as
a pump, in which the hydraulic pump is driven by the running
internal combustion engine, the hydraulic pump sucks hydraulic
fluid via the suction side out of the tank and delivers it into the
delivery line to supply the users of the working hydraulics. If the
hydraulic pump is pressurized on the suction side with hydraulic
fluid under pressure from a hydraulic accumulator, the hydraulic
pump functions as a motor in the same direction of rotation of the
hydrostatic power-unit and in the same direction of flow of the
hydraulic fluid. This makes it possible to generate a torque on the
crankshaft of the internal combustion engine to start the internal
combustion engine for the start-stop function and/or to deliver
additional torque to the crankshaft to supply additional power and
assist the running internal combustion engine by acting as a
booster drive when the internal combustion engine is running.
[0010] The booster drive achieved by operating the hydraulic pump
of the working hydraulics as a motor while the internal combustion
engine is running makes it possible to reduce the power consumption
of the internal combustion engine. As a result of the hydrostatic
booster drive, the output of the internal combustion engine can
also be reduced. A downsizing of the internal combustion engine has
advantages in terms of compliance with emissions regulations.
[0011] With a hydrostatic power-unit operated as a pump and as a
motor in the same direction of rotation and the same direction of
flow of the hydraulic fluid, to operate as a motor, it is necessary
to locate a check valve (that closes in the direction of flow to
the tank) in the suction side of the power-unit. The check valve is
closed when the power-unit is operated as a motor and, thus, makes
possible an increase in pressure in the suction side and prevents
the hydraulic fluid fed from the hydraulic accumulator to the
suction side from flowing back to the tank.
[0012] Hydrostatic power-units in the form of working hydraulic
pumps are known from FIGS. 1 and 2 of WO 2012/125798 A1 and EP 2
308 795 A1. These power-units can be used to supply the users of
the working hydraulics with hydraulic fluid when operated as a
pump, and can be operated in the same direction of rotation as a
motor to function as a hydraulic starter and/or as a booster drive
of the internal combustion engine. To achieve a pressure increase
when operating as a motor, when the suction side of the hydrostatic
power-unit is in communication with a tank and is fed with
hydraulic fluid from a hydraulic accumulator, a check valve that
shuts off the flow in the direction of the tank is located in the
suction side.
[0013] The hydraulic pump, such as an axial piston machine, of the
working hydraulics is generally designed with a high suction limit
speed for operation as a pump. The suction side, which is connected
with the tank when the power-unit is operated as a pump, and the
suction connection of the hydrostatic power-unit therefore have a
relatively large cross section. In FIGS. 1 and 2 of WO 2012/125798
A1 and EP 2 308 795 A1, the check valve located in the suction side
of the hydrostatic power-unit that shuts off the flow to the tank
is a conventional pressure-actuated check valve, for example a ball
check valve. When the power-unit is operated as a pump, the check
valve is actuated into an open position by the suction pressure in
the suction side. However, in the open position during operation of
the power-unit, conventional pressure-actuated check valves create
additional hydraulic resistance in the suction side and create an
additional flow resistance in the suction side of the hydrostatic
power-unit. These cause additional pressure losses in the suction
side of the hydrostatic power-unit, which reduce the suction limit
speed of the power-unit when it is operated as a pump.
SUMMARY OF THE INVENTION
[0014] An object of this invention is to provide a check valve in
the suction side of a hydrostatic power-unit operable in the same
direction of rotation as a pump and as a motor, such that when the
power-unit is operated as a motor, hydraulic fluid is fed to the
power-unit from a hydraulic accumulator on the suction side, and
when the power-unit is operated as a pump with an open check valve
device, there is no adverse effect on the suction limit speed of
the power-unit.
[0015] This object is accomplished in that the check valve device
of the invention has a check valve that can be actuated by an
actuator device. The actuator device can actively actuate the check
valve between a closed position, in which a connection between the
suction side and the tank is cut off in the direction of flow from
the suction side to the tank; and an open position, in which the
connection between the suction side and the tank is opened. A check
valve that can be actively actuated between a closed position and
an open position by an actuator device has the advantage over
pressure-actuated check valves of the known art in that the check
valve can be designed so that in the open position the check valve
does not represent any additional hydraulic resistance in the
suction side and, therefore, causes no additional flow resistance
in the suction side. With the check valve of the invention that can
be actively controlled by the actuator device, it becomes possible
for a hydrostatic power-unit (which, when operated as a pump,
supplies a user such as the working hydraulic system) to be
operated as a motor so that the power-unit functions as a hydraulic
starter of the internal combustion engine and/or as a booster drive
to assist the internal combustion engine without causing a reduced
suction limit speed when operated as a pump.
[0016] In one preferred embodiment of the invention, the check
valve can be actuated by the actuator device into the open position
when the power-unit is operated as a pump and into the closed
position when the power-unit is operated as a motor. The actuator
device makes it possible in a simple manner to actively move the
check valve into the open position when the power-unit is operated
as a pump, to achieve pump operation of the hydrostatic power-unit
without creating additional flow resistance in the suction side,
and to actively actuate the check valve into the closed position
for operation of the hydrostatic power-unit as a motor to provide a
drive by the power-unit by means of the hydraulic fluid fed to the
suction side from the hydraulic accumulator.
[0017] It is particularly advantageous if the check valve can be
actuated by a spring device into the closed position, and the check
valve can be actuated into the open position by a hydraulic
actuation pressure applied to the actuator device. A simple control
and actuation of the check valve can be achieved with a hydrostatic
control system with this type of actuator device. Additional
advantages are achieved if the actuator pressure is generated only
when the internal combustion engine is running. When the internal
combustion engine is shut off and there is no actuation pressure,
the check valve is actuated by the spring device into the closed
position, so that when the hydrostatic power-unit is used as a
hydraulic starter of the internal combustion engine, the power-unit
can be immediately operated as a motor during startup of the
internal combustion engine without having to first actuate the
check valve into the closed position.
[0018] In one preferred embodiment of the invention, the check
valve in the closed position is acted upon by the pressure from the
hydraulic accumulator connected on the suction side into the closed
position. As a result, the check valve is held in the closed
position by the pressure from the hydraulic accumulator on the
suction side for the duration of the startup of the internal
combustion engine. This prevents the check valve from being
actuated into the open position before the end of the startup
process by the actuation pressure generated when the internal
combustion engine is running.
[0019] In one preferred embodiment of the invention, the actuator
device is a positioning piston in an operative connection with the
check valve. With a positioning piston, it is possible in a simple
manner to achieve an active actuation of the check valve between
the closed position and the open position.
[0020] In one advantageous embodiment of the invention, the
positioning piston is actuated by the spring device and has a
piston pressure chamber that can be pressurized with the actuation
pressure and counteracts the spring device. It thereby becomes
possible with little construction effort or expense for the check
valve to be actuated into the closed position by the spring device
and into the open position by the actuation pressure.
[0021] The spring device is advantageously located in a spring-side
piston pressure chamber of the positioning piston, which can be
placed in communication with the tank. When the actuation pressure
is present, the positioning piston can be moved against the
pressure of the spring device, and the check valve can be actuated
into the open position.
[0022] In an alternative embodiment of the invention, the actuator
device is a control pressure surface located on the check valve and
can be actuated by the hydraulic actuation pressure, which actuates
the check valve toward the open position. With a control pressure
surface on the check valve, an active actuation of the check valve
between the closed position and the open position can be achieved
and it can be achieved in a simple manner and with little
construction effort and expense that the check valve can be
actuated into the closed position by the spring device and into the
open position by the actuation pressure.
[0023] In one advantageous embodiment of the invention, the check
valve is a flapper valve with a pivotable flapper, which is in an
operative connection with the actuator device. A flapper valve
makes possible a compact and space-saving construction of the check
valve and can, with little construction effort or expense, be
actuated with an actuator device in the form of a positioning
piston. With a flapper valve, it is possible to hold the flapper
valve in the closed position in a simple manner during startup of
the internal combustion engine by the pressure of the hydraulic
accumulator present on the suction side of the power-unit.
[0024] In one embodiment of the invention, the positioning piston
can be in an operative connection with the flapper through the
interposition of a tie rod, such as a swing arm, which is connected
in an articulated manner to the flapper and to the positioning
piston. With a tie rod connected in an articulated manner, the
pivotable flap of the flapper valve can be actuated in a simple
manner by the linear movement of the positioning piston.
[0025] As an alternative to an interposed tie rod, the positioning
piston can be connected directly in an articulated manner with the
flapper, with the articulated connection comprising a slot. If the
articulated connection between the positioning piston and the
pivotable flapper comprises a slot, it is also possible to actuate
the pivotable flapper of the flapper valve by a linear movement of
the positioning piston.
[0026] It is particularly advantageous if the flapper is located in
a suction channel so that it can pivot and also so that the flapper
does not project into the suction channel when in the open
position. Consequently, the flapper in the open position does not
cause any additional hydraulic resistance and no additional flow
resistance in the suction side of the power-unit during its
operation as a pump.
[0027] In one alternative embodiment of the invention, the check
valve is a valve with a flat slider that can move longitudinally
and is in an operational connection with the actuator device. A
valve with a flat slider also makes possible a compact and
space-saving construction of the check valve and can, with little
construction effort or expense, be actuated with an actuator device
in the form of a positioning piston or a control pressure surface.
In addition, with a valve with a flat slider, the slider in the
open position does not cause any additional flow resistance in the
suction side of the power-unit during operation as a pump.
[0028] In an additional alternative embodiment of the invention,
the check valve is a piston spool valve with a piston that can be
displaced longitudinally or can be rotated and is in an operative
connection with the actuator device. A piston spool valve also
makes possible a compact and space-saving construction of the check
valve and can be actuated with little construction effort or
expense with an actuator device in the form of a positioning piston
or a control pressure surface. In addition, on a piston spool
valve, the preferably cylindrical piston, when in the open
position, causes no additional flow resistance in the suction side
of the power-unit during operation as a pump.
[0029] Alternatively, the check valve can be a ball valve with a
rotatable ball and in an operative connection with the actuator
device. A ball valve also makes possible a compact and space-saving
construction of the check valve and can be actuated with little
construction effort or expense with an actuator device in the form
of a positioning piston or a control pressure surface. In addition,
with a ball valve, it is possible in a simple manner to ensure that
the ball, in the open position, creates no additional flow
resistance in the suction side of the power-unit during operation
as a pump.
[0030] The invention further relates to a hydrostatic power-unit
which can be in a drive connection with an internal combustion
engine and can be operated as a pump or as a motor. The power-unit,
when operated as a pump, sucks hydraulic fluid on a suction side
from a tank and delivers to the delivery side. When operated as a
motor, the power-unit is driven by hydraulic fluid under pressure
fed from a hydraulic accumulator via the suction side (which is in
communication with the tank). A check valve device of the invention
is located in the suction side of the power-unit. With a check
valve device of the invention located in the suction side of the
power-unit, and actively actuable with the actuator device between
the closed position and the open position, the power-unit can be
operated as a motor with little additional effort and expense so
that the power-unit can be used as a hydraulic starter for the
internal combustion engine to achieve a start-stop function and/or
as a booster drive to assist the running internal combustion
engine.
[0031] The suction side of the hydrostatic power-unit can be a
suction channel or suction line.
[0032] In one embodiment of the invention, the check valve device
is installed in a housing of the power-unit. The check valve device
can be integrated into the housing of the power-unit with little
construction effort and can be located in the segment of the
suction channel that is in the housing.
[0033] Alternatively, the check valve device can have an
independent housing. It thereby becomes possible in a simple matter
to add the check valve device of the invention to an existing
power-unit to achieve the additional operation of the power-unit as
a motor so that it can function as a hydraulic starter and/or
function as a booster drive.
[0034] The housing of the check valve can be connected by a flange
to the housing of the power-unit. If the housing of the check valve
device is constructed so that it can be connected by a flange to
the housing of the power-unit in the area of the suction
connection, an existing power-unit can be provided with the check
valve of the invention with little additional construction effort
or expense to make it possible to additionally operate the
power-unit as a motor to function as a hydraulic starter and/or a
booster drive.
[0035] If a control valve is provided to control the connection of
the hydraulic accumulator with the suction side of the power-unit
for operation as a motor, it is possible in a simple manner to
connect the suction side of the power-unit operating as a motor
with the hydraulic accumulator.
[0036] The power-unit can be a constant displacement power-unit,
i.e., a power-unit with a constant displacement volume.
[0037] Alternatively, the power-unit can be a variable displacement
power-unit in which the displacement volume can be varied by a
displacement volume control device actuated by a control device.
The control device can be connected to a charging pressure circuit
to supply it with hydraulic fluid and can be connected with the
hydraulic accumulator. A hydraulic or electro-hydraulic control
device can be supplied in a simple manner with hydraulic fluid by
the connection with the charging pressure circuit and/or the
hydraulic accumulator for variation and actuation of the
displacement volume control device. The connection of the control
device with the hydraulic accumulator makes it possible in a simple
matter, when the power-unit is operated as a motor and as a
hydraulic starter, to vary the displacement volume of the
displacement volume control device of the power-unit during startup
of the shut-off internal combustion engine toward the maximum
displacement volume with hydraulic fluid from the charged hydraulic
accumulator, thus generating an appropriate torque to start the
internal combustion engine from the hydraulic fluid flowing to the
suction side from the hydraulic accumulator.
[0038] It is particularly advantageous to install a shutoff valve,
in particular a check valve that shuts off the flow to the charging
pressure circuit, in the connection between the control device and
the charging pressure circuit. With a check valve of this type,
during startup of the shut-off internal combustion engine, it is
possible to supply only the control device of the power-unit with
hydraulic fluid from the hydraulic accumulator and to isolate the
other users of the charging pressure circuit from the hydraulic
accumulator. Thus, the hydraulic fluid present in the hydraulic
accumulator is effectively available for the operation of the
power-unit as a motor.
[0039] For this purpose, the hydraulic accumulator is
advantageously in communication with the suction side of the
power-unit by a connecting line in which the control valve is
located. To supply the control device with hydraulic fluid from the
hydraulic accumulator, a hydraulic line is connected to the
connecting line between the control valve and the suction side of
the power-unit. By means of a connection of this type which
supplies the control device with hydraulic fluid from the hydraulic
accumulator, it becomes possible in a simple manner with a
corresponding actuation of the control valve into an open position
for the operation of the power-unit as a motor during a startup of
the internal combustion engine, to also supply the control device
of the variable displacement volume control device of the
power-unit with hydraulic fluid to achieve an adjustment of the
displacement volume control device of the power-unit toward the
maximum displacement volume.
[0040] The hydraulic line is particularly advantageously connected
to a control pressure line that runs from the charging pressure
circuit to the control device. The shutoff valve is located in the
control pressure line. The hydraulic line is connected to the
control pressure line between the shutoff valve and the control
device. With the connection of the hydraulic line to the control
pressure line equipped with the shut off valve, it is possible in a
simple manner during a startup of the internal combustion engine to
supply only the control device of the power-unit with hydraulic
fluid from the hydraulic accumulator.
[0041] A pressure reducer valve is advantageously located in the
hydraulic line, with which, with little additional construction
effort or expense, the pressure level in the hydraulic accumulator
can be reduced to the level of the charge pressure for the supply
of the control device of the power-unit.
[0042] The charge pressure of a charging pressure circuit is
particularly advantageously the actuation pressure of the actuator
device of the check valve. Consequently, it becomes possible, in a
simple manner and with little added construction effort or expense,
to achieve a hydrostatic actuation of the actuator device and,
thus, of the check valve.
[0043] For this purpose, there is advantageously a branch line that
runs from the hydraulic line to the actuator device. Between the
pressure reducer valve and the connection of the branch line, there
is a shutoff valve, in particular a check valve, that shuts off the
flow to the pressure reducer valve. With a branch line that
branches off from the hydraulic line, during the start-up process,
the charge pressure generated via the pressure reducer valve is
present in the branch line. After the start-up process, when the
internal combustion engine is running, the charge pressure of the
charging pressure circuit can pressurize the actuator device to
actuate the check valve into the open position and to hold it in
the open position to allow operation as a pump.
[0044] In one embodiment of the invention, the piston pressure
chamber of the positioning piston is in communication with the
charging pressure circuit and the spring-side piston pressure
chamber of the positioning piston is depressurized to the tank.
With a connection of the positioning piston of this type, it is
possible, without additional control valves and control logic, to
provide operational functionality of the check valve for use of the
power-unit as a motor to be a hydraulic starter of the internal
combustion engine. The check valve, with the internal combustion
engine shut off, is actuated by the spring device into the closed
position. When the internal combustion engine is running, the check
valve is actuated by the charge pressure generated by the charging
pressure circuit into the open position.
[0045] In an alternative embodiment of the invention, the control
pressure surface of the check valve is in communication with the
charging pressure circuit. An additional control pressure surface
is formed on the check valve, which actuates the check valve toward
the closed position. For pressurization, the additional control
pressure surface can be connected with the suction side between the
power-unit and the check valve. With control pressure surfaces of
this type on the check valve, it becomes possible, without
additional control valves and control logic, to achieve functional
operation of the check valve for use of the power-unit as a motor,
i.e., as a hydraulic starter for the internal combustion engine.
The check valve, with the internal combustion engine shut off, is
actuated by the spring device into the closed position. When the
internal combustion engine is running, the check valve is actuated
into the open position by the charge pressure generated by the
charging pressure circuit. With the additional control pressure
surface, it is guaranteed that the check valve, in the closed
position, is held in the closed position during startup of the
internal combustion engine by the pressure of the hydraulic
accumulator present at the suction side of the power-unit.
[0046] In one preferred embodiment of the invention, to control the
pressurization of the actuator device, a switching valve is
provided. In a first switched position, the check valve can be
actuated into the open position as a function of the actuation
pressure and, in a second switched position, the check valve can be
actuated into the closed position. In the first switched position
of the switching valve, the functionality of the switch valve is
therefore achieved for the use of the power-unit (operated as a
motor) as a hydraulic starter for the internal combustion engine.
In the second switched position of the switching valve, when the
internal combustion engine is running, the check valve can be
actuated into the closed position to achieve a functionality of the
check valve for use of the power-unit (operating as a motor) as a
booster drive for the running internal combustion engine.
[0047] When the actuator device is in the form of a positioning
piston, in the first switched position of the switching valve, the
piston pressure chamber of the positioning piston is pressurized at
the actuation pressure, and the spring-side piston pressure chamber
is depressurized to the tank. In the second switched position of
the switch valve, the spring-side piston pressure chamber of the
positioning piston is pressurized with the actuation pressure, and
the piston pressure chamber is depressurized to the tank. In the
first switched position of the switching valve, the check valve
makes it possible to use the power-unit (operating as a motor) as a
hydraulic starter for the internal combustion engine. In the second
switched position of the switching valve, when the internal
combustion engine is running, the check valve can be actuated into
the closed position by the charge pressure pressurizing the
spring-side piston pressure chamber of the positioning piston, to
achieve a functionality of the check valve for use of the
power-unit (operated as a motor) as a booster drive for the running
internal combustion engine.
[0048] When the actuator device is in the form of a control
pressure surface, if in the first switched position of the
switching valve the control pressure surface of the check valve is
pressurized with the actuation pressure, and the additional control
pressure surface of the check valve is in communication with the
suction side between the power-unit and the check valve, the
functionality of the check valve can be achieved in a simple manner
for the use of the power-unit (operated as a motor) as a hydraulic
starter for the internal combustion engine.
[0049] In one embodiment of the invention, in the second switched
position of the switching valve, the control pressure surface and
the additional control pressure surface of the check valve are
pressurized with the actuation pressure. In the second switched
position of the switching valve, it thereby becomes possible, when
the internal combustion engine is running, to actuate the check
valve by the spring device into the closed position, so that the
functionality of the check valve can be achieved for use of the
power-unit (operated as a motor) as a booster drive for the running
internal combustion engine.
[0050] In an alternative embodiment of the invention, in the second
switched position of the switching valve, the control pressure
surface is depressurized to a tank and the additional control
pressure surface is pressurized with the actuation pressure. In the
second switched position of the switching valve, it thereby becomes
possible, when the internal combustion engine is running, to
actuate the check valve into the closed position by the charge
pressure present at the other control pressure surface, so that the
functionality of the check valve for use of the power-unit
(operating as a motor) as a booster drive can be easily achieved
when the internal combustion engine is running.
[0051] For this purpose, in the closed position of the check valve,
there is advantageously a connection of the suction side with the
tank in the direction of flow from the tank to the suction side, in
particular by means of a check valve, so that the power-unit
(operating as a booster drive) can continue to suck hydraulic fluid
from the tank with the suction side.
[0052] It is advantageous in terms of a simple construction if the
control valve and/or the pressure reducer valve and/or the
switching valve is/are located in the housing of the check
valve.
[0053] The control valve and/or the switching valve are
advantageously actuated electrically and are in an operative
connection with an electronic control device for actuation.
[0054] If the electronic control device is in communication with a
sensor device that measures the speed of rotation of the internal
combustion engine and/or the pressure of the hydraulic accumulator,
it is easily possible, by means of appropriate operating strategies
stored in the control device, to control the operation of the
power-unit as a motor to function as a hydraulic starter of the
internal combustion engine and/or as a booster drive of the
internal combustion engine by a corresponding actuation of the
switched valve and of the switching valve.
[0055] The invention further relates to a hydrostatic drive system
with a hydrostatic power-unit of the invention in a drive
connection with an internal combustion engine. The hydrostatic
power-unit can be operated as a pump and as a motor in the same
direction of rotation. When operated as a pump, the power-unit
supplies at least one user, in particular a working hydraulics
system, and, when operated as a motor, functions as a hydraulic
starter for a start-stop function of the internal combustion engine
and/or as a hydraulic booster drive when the internal combustion
engine is running. With the check valve device of the invention, in
a drive system with a power-unit used as a hydraulic work pump, the
power-unit can be operated as a motor driven by hydraulic fluid
from a hydraulic accumulator in a simple manner and without
reducing the suction limit speed in pump operation. When operated
as a motor, the power-unit is supplied with hydraulic fluid from a
hydraulic accumulator, so that a start-stop function and/or a
booster drive can be achieved in a low-loss, robust, economical,
and structurally simple manner using the hydraulic work pump, which
is already present in the drivetrain.
[0056] For this purpose, for the start-stop function of the
internal combustion engine, when the internal combustion engine is
shut off, the check valve is advantageously actuated by the spring
device into the closed position. After startup of the internal
combustion engine by operating the hydrostatic power-unit as a
motor, the check valve can be actuated into the open position by
the hydraulic actuation pressure generated at the actuator device
when the internal combustion engine is running. For the use of the
power-unit as a hydraulic starter of the internal combustion
engine, it is therefore possible in a simple manner for the check
valve to be in the closed position and, thus, there is no actuation
pressure when the internal combustion engine is shut off. The
power-unit can be immediately operated as a motor by means of the
control valve to start the internal combustion engine without
having to first move the check valve into the closed position.
After successfully completed startup of the internal combustion
engine, in which case the actuation pressure is already achieved
during the starting process, the check valve is automatically
actuated into the open position so that the users of the working
hydraulics can be supplied with hydraulic fluid by operating the
power-unit as a pump.
[0057] To provide the booster drive when the internal combustion
engine is running, the check valve can advantageously be actuated
into the closed position by the hydraulic actuation pressure for
the duration of operation of the booster drive.
[0058] The invention further relates to a vehicle, in particular a
mobile machine with a hydrostatic drive system of the invention. On
a vehicle with a hydraulic work pump already present, the check
valve device of the invention allows for a start-stop function
and/or a booster drive of the internal combustion engine to be
easily achieved using the existing hydraulic work pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0059] Additional advantages and details of the invention are
explained below with reference to the exemplary embodiments
illustrated in the accompanying schematic figures, in which like
reference numbers identify like parts throughout.
[0060] FIG. 1 shows a first embodiment of the invention;
[0061] FIG. 2 shows a second embodiment of the invention;
[0062] FIG. 3 shows a third embodiment of the invention;
[0063] FIG. 4 shows a development of the invention illustrated in
FIG. 1;
[0064] FIG. 5 shows a development of the invention illustrated in
FIG. 3; and
[0065] FIG. 6 shows an additional development of the invention
illustrated in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0066] FIG. 1 is a schematic circuit diagram of a hydrostatic drive
system 1 of the invention in the drivetrain of a vehicle, for
example, a mobile machine in the form of an industrial truck or
construction or agricultural equipment.
[0067] The drive system 1 of the invention comprises an internal
combustion engine 2, such as a diesel engine, a traction drive 3
driven by the internal combustion engine 2, and working hydraulics
4 driven by the internal combustion engine 2.
[0068] In the illustrated exemplary embodiment, the traction drive
3 is a hydrostatic traction drive, which includes a continuously
variable displacement traction pump 5 as the primary unit. The
traction pump 5 is in a drive connection to drive an output shaft 6
of the internal combustion engine 2. The traction pump 5 is in
communication with one or more fixed displacement or variable
displacement hydraulic motors (not illustrated in further detail)
as secondary units in a closed circuit, which secondary units are
in an operative connection with the driven wheels of the vehicle in
a manner not illustrated in any further detail.
[0069] Alternatively, the traction drive 3 can be an electric
traction drive with an electric generator driven by the internal
combustion engine 2 as the primary unit and one or more electrical
traction motors as secondary units. In addition, the traction drive
3 can be a mechanical traction drive with a mechanical
transmission, such as a continuously variable transmission or a
power split transmission or a torque converter transmission, for
example.
[0070] The working hydraulics 4 comprise the work functions of the
machine, such as, on an industrial truck, for example, the working
hydraulics 4 to actuate load holding means on a lifting mast or, on
construction equipment in the form of an excavator or a wheeled
loader, the work functions of the working equipment can be in the
form of a shovel.
[0071] To supply the work functions (and therefore the users) with
hydraulic fluid, the working hydraulics system 4 comprises a
hydrostatic power-unit 7. The power-unit 7 is operated in an open
circuit and is in a drive connection with the output shaft 6 of the
internal combustion engine 2.
[0072] The power-unit 7 can be a constant displacement power-unit
with a constant displacement volume. In the illustrated exemplary
embodiment, the power-unit 7 is a variable displacement power-unit
with a continuously variable displacement volume, for example an
axial piston machine utilizing a swashplate construction.
[0073] The power-unit 7 is operated in an open circuit and is in
communication on the input side with a tank 9 by means of the
suction connection and a suction line or a suction channel 8, which
form a suction side S. A delivery line 10 is in communication on
the output side with the delivery connection and a delivery side P
of the power-unit 7 and is connected to a control valve device 11,
by means of which the hydraulic users (which are not illustrated in
detail) of the working hydraulics 4 can be controlled. The control
valve device 11 preferably comprises one or more directional
control valves for the actuation of the users, which users can also
include a hydraulic steering device of the vehicle.
[0074] The drive system 1 further comprises a charge pump 15 driven
by a connection with the output shaft 6. In the illustrated
exemplary embodiment, the charge pump 15 is a constant displacement
pump with a constant displacement volume and is operated in an open
circuit. The charge pump 15 is in communication on the suction side
with the tank 9 by a suction line 16 and delivers into a charge
pressure line 17 connected to the delivery side, to which the
corresponding users of a charging pressure circuit 18 are
connected, such as, control devices to vary the displacement volume
of the traction pump 5 and of the power-unit 7, a feed device for
the hydrostatic traction drive 3, a brake system of the vehicle,
and pilot valves for the control valves of the working hydraulics
4. When the internal combustion engine 2 is running, the charge
pump 15 generates a constant charge pressure in the charging
pressure circuit 18. To ensure the constant charge pressure in the
charging pressure circuit 18, the charge pressure line 17 is
associated with a pressure limiting device, such as a pressure
limiting valve.
[0075] On the drive train 1 of the invention, the hydrostatic
power-unit 7 of the working hydraulics 4 is a two-quadrant
power-unit, which can be operated as a pump and as a motor in the
same direction of rotation and the same direction of flow of the
hydraulic fluid.
[0076] When operated as a pump, in which case the power-unit 7 is
driven by the running internal combustion engine 2, the power-unit
7 sucks hydraulic fluid via the suction line 8 from the tank 9 and
delivers the hydraulic fluid into the delivery line 10 to supply
the users of the working hydraulics 4. The power-unit 7, when
operated as a pump, also charges a hydraulic accumulator 20, which
can be connected to the delivery line 10 by a charge valve 21 and a
charge line 22. To charge the hydraulic accumulator 20, the
power-unit 7 operating as a pump can optionally be driven with the
kinetic energy absorbed from the vehicle, which increases as the
vehicle decelerates, or it can also be driven on the primary side
by the running internal combustion engine 2.
[0077] When the power-unit 7 is operated as a motor, in which the
power-unit 7 acts as a hydraulic starter to provide a start-stop
function to start the internal combustion engine 2, the power-unit
7 is driven on the suction side S with hydraulic fluid from the
hydraulic accumulator 20.
[0078] The connection of the hydraulic accumulator 20 with the
suction side S of the power-unit 7 for the operation of the
power-unit 7 as a motor can be controlled by an electrically
actuated control valve 25. The control valve 25 has a closed
position 25a and an open position 25b. The closed position 25a is
preferably leak-tight, with a shutoff valve that shuts off the flow
to the power-unit 7. The control valve 25 is an electrically
actuated control valve, preferably a switching valve, which can be
actuated between the closed position 25a and the open position 25b
by an electrical actuator device 26, such as a switch magnet.
[0079] For its actuation, the actuator device 26 is in
communication with an electronic control device 27. To monitor the
accumulator charge pressure and, thus, the accumulator status of
the hydraulic accumulator 20, there is a pressure sensor device 28
which is in communication with the control device 27. The
electronic control device 27 is also in communication with a speed
sensor device 29 that measures the speed of rotation of the
internal combustion engine 2. The control device 27 can also
actuate the charge valve 21 for charging the hydraulic accumulator
20.
[0080] The control valve 25 is located in a connecting line 23 that
runs from the hydraulic accumulator 20 to the suction line 8 and is
connected to the suction line 8.
[0081] A check valve device 30 of the invention is located in the
suction line 8 of the power-unit 7, between the connection of the
connecting line 23 and the tank 9. When the power-unit 7 is
operated as a motor, the check valve device 30 makes possible a
pressure increase on the suction side S. The check valve device 30
has a check valve 32 that can be actuated by an actuator device 31.
By means of the actuator device 31, the check valve 32 can be
actively switched between a closed position 32a (illustrated in
FIG. 1) in which the communication between the suction side S and
the tank 9 in the direction of flow from the suction side S to the
tank 9 is shut off, and an open position 32b (illustrated in broken
lines in FIG. 1) in which the communication between the suction
side S and the tank 9 is opened.
[0082] To adjust the displacement volume, the power-unit 7, which
in the illustrated exemplary embodiment is in the form of a
variable displacement power-unit with a continuously variable
displacement volume, has a displacement volume control device 40,
such as a variable-inclination swashplate of an axial piston
machine utilizing a swashplate construction. For actuation, the
displacement volume control device 40 has a positioning piston
device 41 in an operative connection with the displacement volume
control device 40. The power-unit 7 is a unilaterally variable
power-unit in which the displacement volume control device 40,
beginning from a position with a minimum displacement volume, can
be adjusted in a control position or pivoting direction into a
position with maximum displacement volume. The positioning piston
device 41 has a control pressure compartment 41a that acts in the
direction of the maximum displacement volume and a control pressure
compartment 41b which acts in the direction of the minimum
displacement volume.
[0083] The displacement volume control device 40 can be actuated by
a control device 42. The control device 42 has a control valve (not
illustrated in detail), by means of which the pressurization of the
control pressure compartments 41a, 41b can be controlled with a
control pressure or by their depressurization to the tank 9.
[0084] To supply hydraulic fluid and to generate a control pressure
in the control pressure chambers 41a and 41b, the control device 42
is in communication via a control pressure line 43 with the charge
pressure line 17 and, thus, with the charging pressure circuit 18.
The control device 42 also has a connection to a tank line 44 that
leads to the tank 9. The control device 42 is preferably actuated
electrically and for this purpose is in communication with the
electronic control device 27. In the illustrated exemplary
embodiment, the control device 44 comprises a control valve, with a
mechanical feedback 46 of the current position of the displacement
volume control device 40 to the control device 42. There is also a
spring device 45 in the form of a compression spring which acts on
the displacement volume control device 40 in the direction of the
minimum displacement volume. The spring device can be limited by a
corresponding stop on the displacement volume control device
40.
[0085] To pressurize the displacement volume control device 40 into
the position with maximum displacement volume during a startup of
the shut-off internal combustion engine 2 by operating the
power-unit 7 as a motor, the control device 42 can also be
connected to the hydraulic accumulator 20 to supply hydraulic fluid
and, thus, to generate a control pressure. For this purpose, a
hydraulic line 50 is provided that runs from the control pressure
line 43 to the connecting line 23. A pressure reducer valve 51 is
located in the hydraulic line 50. The hydraulic line 50 is
connected to the connecting line 23 between the control valve 25
and the suction line 8.
[0086] A shutoff valve 52 is also located in the connection between
the control device 42 and the charging pressure circuit 18. The
hydraulic line 50 is connected to the control pressure line 43
between the shutoff valve 52 and the control device 42. In the
illustrated exemplary embodiment, the shutoff valve 52 is a check
valve 53 that opens to allow flow to the control device 42.
[0087] In FIG. 1, the check valve 32 of the invention located in
the suction line 8 is a flapper valve 33 with a flapper 34 that can
pivot around a pivoting axis 35. The flapper 34 is in an operative
connection for actuation with the actuator device 31.
[0088] The actuator device 31 of the check valve 32 of the
invention is a longitudinally displaceable positioning piston 36.
The positioning piston 36 has a piston rod 36c in a drive
connection with the flapper 34. In FIG. 1, the piston rod 36c of
the positioning piston 36 is in operative connection with the
flapper 34 via the interposition of a tie rod 37, such as a swing
arm, which is connected in an articulated manner to the flapper 34
and in an articulated manner to the piston rod 36c of the
positioning piston 36.
[0089] The positioning piston 36 is located so that it can move
longitudinally in a cylinder housing, in which there is a piston
pressure chamber 36a that pressurizes the positioning piston 36
toward the illustrated closed position 32a of the check valve 32
and a piston pressure chamber 36b that pressurizes the positioning
piston 36 into the opening position 32b of the check valve 32.
There is a spring device 38, such as a compression spring, in the
piston pressure chamber 36a that acts on the positioning piston 36
and, thus, actuates the check valve 32 into the closed position
32a. The piston pressure chamber 36a provided with the spring
device 38 is connected with the tank 9 by a depressurization line
39.
[0090] The check valve 32 of the invention can be actuated into the
open position 32b by a hydraulic actuation pressure which
pressurizes the actuator device 31. In the illustrated exemplary
embodiment, the actuation pressure is formed by the constant charge
pressure of the charging pressure circuit 18, for which purpose a
branch line 60 that branches off the hydraulic line 50 or the
control pressure line 43 is connected to the piston pressure
chamber 36b of the positioning piston 36 that acts in the opening
direction. Between the pressure reducer valve 51 located in the
hydraulic line 50 and the connection of the branch line 60, there
is a shut-off valve 61 which, in the illustrated exemplary
embodiment, is a check valve 62 that shuts off the flow to the
pressure reducer valve 51.
[0091] The flapper 34 of the flapper valve 33, in the illustrated
closed position 32a, actuates a valve seat 65 in the suction line 8
which, for this purpose, is a suction channel, at least in the
vicinity of the valve seat 65.
[0092] The pivoting axis 35 of the flapper 34 is oriented in the
radial direction outside a diameter D of the suction line 8 so that
in the open position 32b (and, thus, the open switched position),
the flapper 34 does not protrude into the suction line 8 and, in
the open position 32b, does not cause any additional hydraulic
resistance and, thus, flow resistance in the suction line 8. For
this purpose, there is a radial expansion 66 in the suction line 8
in the form of a suction channel, into which the flapper 34
preferably pivots all the way in the open position 32b.
[0093] The check valve device 30 of the invention can be installed
in the housing of the power-unit 7. In the illustrated exemplary
embodiment, the check valve device 30 has a separate housing 70
which forms a section of the suction line 8. The control valve 25
and the pressure reducer valve 51 can also be installed in the
housing 70 (indicated by the broken line in FIG. 1) of the check
valve device 30. The housing 70 can preferably be connected and
attached by a flange to the suction connection of the power-unit 7.
Alternatively, this housing 70 can be installed separately from the
power-unit 7 in any desired location in the suction line 8 inside
the vehicle.
[0094] The drive system 1 in FIG. 1, in which the power-unit 7
operated as a motor can be used as a hydraulic starter of the
internal combustion engine 2 for a start-stop function, works as
follows.
[0095] With the internal combustion engine 2 shut off and the
charge pump 15 not being driven, and with the control valve 25 in
the closed position 25a, the charge pressure present in the control
pressure line 43 and the hydraulic line 50 connected to it (and,
thus, the actuation pressure of the positioning piston 36 present
in the piston pressure chamber 36b) drops so that the flapper 34 is
actuated by the positioning piston 36, which is pushed by the
spring device 38 in the closing direction into the closed position
32a illustrated in FIG. 1. As a result of the drop in the charge
pressure when the internal combustion engine 2 is shut off, the
power-unit 7 is set to the position with the minimum displacement
volume. In the closed position 32a, the flapper 34 is held against
the valve seat 65 by the spring device 38 with a defined force. In
the closed position 32a, the connection between the suction side S
of the power-unit 7 in the direction of flow to the tank 9 is cut
off. For the startup of the internal combustion engine 2, the
control valve 25 (when the hydraulic accumulator is charged) is
actuated into the open position 25b. Thus, the suction line 8 is
pressurized with the pressure and hydraulic fluid of the hydraulic
accumulator 20 for the operation of the power-unit 7 as a motor. In
the open position 25b of the control valve 25, the control device
42 of the power-unit 7 is supplied with the charge pressure by the
pressure reducer valve 51 so that the power-unit 7 can be set in
the direction of the maximum displacement volume. The shutoff valve
52 in the control pressure line 43 ensures that, during a startup
process of the internal combustion engine 2, only the control
device 42 of the power-unit 7 is supplied with a charge pressure
from the hydraulic accumulator 20 via the pressure reducer valve 51
and prevents the charge pressure generated from the hydraulic
accumulator 20 from being supplied to the other users of the
charging pressure circuit 18 during the startup process. Once the
torque resulting from the displacement volume and the pressure
present in the suction side S of the power-unit 7 overcome the
torque resulting from the adhesive friction of the output shaft 6
and the units connected to it, the startup of the internal
combustion engine 2 takes place.
[0096] By means of the branch line 60, the charge pressure
generated at the pressure reducer valve 51 is present in the piston
pressure chamber 36b of the positioning piston 36 and generates a
force on the positioning piston 36 acting in the direction of the
open position of the flapper 34. However, the force acting from the
pressure of the hydraulic accumulator 20 (and, thus, the pressure
in the suction line) on the flapper 34 toward the closed position
32a is greater than the opening force on the positioning piston 36,
so that the flapper 34 is held in the closed position 32a during
the startup process of the engine 2 and the operation of the
power-unit 7 as a motor.
[0097] If a speed of rotation that indicates a successful startup
process is detected by the speed sensor 29, the control valve 25 is
actuated into the closed position 25a and the operation of the
power-unit 7 as a motor is ended. Consequently, the pressure of the
hydraulic accumulator 20 acting on the flapper 34 in the closing
direction drops. With the startup process of the internal
combustion engine 2, a constant charge pressure is built up in the
control pressure line 43 via the driven charge pump 15 and is
present in the piston pressure chamber 36b of the positioning
piston 36 via the hydraulic line 50 and the branch line 60, so that
the flapper 34 can be actuated by the positioning piston 36 into
the open position 32b.
[0098] When the flapper 34 is in the open position 32b, the
power-unit 7 driven by the internal combustion engine 2 can be used
as a pump to supply the users of the working hydraulics 4. The
flapper 34 in the open position 32b in the suction line 8 does not
cause any additional hydraulic resistance or flow resistance, which
reduces the suction limit speed of the power-unit 7 when operated
as a pump.
[0099] FIG. 2 shows a second exemplary embodiment of the invention.
Identical components are identified by the same reference
numbers.
[0100] FIG. 2 differs from FIG. 1 with regard to the construction
of the check valve 32 of the invention. The check valve 32 in FIG.
2 is a piston or flat slide valve 80 with a longitudinally
displaceable piston or slide 81, which for actuation is in an
operative connection with the actuator device 31 (which is
analogous to the one illustrated in FIG. 1). The piston or slide 81
can be actuated into the open position 32b by the actuator device
31 by the actuator pressure (in the form of the charge pressure)
and can be actuated into the closed position 32a by the spring
device 38 when the internal combustion engine 2 is shut off.
[0101] To hold the check valve 32 (e.g., a piston or flat slide
valve 80) in the closed position 32a for the duration of the
startup process of the internal combustion engine 2 and to prevent
the actuation of the check valve 32 before the end of the startup
process of the internal combustion engine 2 by the charge pressure
generated in the branch line 60 against the force of the spring
device 38 into the open position 32b, there is an additional
control pressure surface 100 on the check valve 32 that acts in the
direction of the closed position 32a, which during a startup of the
internal combustion engine 2 is pressurized by the pressure of the
hydraulic accumulator 20 and, thus, the pressure in the suction
line 8. For this purpose, there is a control pressure line 101
which is in communication with the control pressure surface 100,
which in the illustrated exemplary embodiment is connected to the
connecting line 23 between the control valve 25 in the suction line
8.
[0102] The piston or slide 81 is located in the suction line 8 such
that, in the open position 32b, it presents no additional flow
resistance in the suction side S for the hydraulic fluid sucked in
by the power-unit 7 operating as a pump.
[0103] As an alternative to a construction of the check valve 32 as
a flat slide valve 80, the check valve 32 in FIG. 2 can be a piston
slide valve with a longitudinally displaceable (and preferably
cylindrical) piston, which for actuation is in an operative
connection with the actuator device 31. The check valve can also be
in the form of a ball valve.
[0104] FIG. 3 illustrates a third exemplary embodiment of the
invention. The same components are identified by the same reference
numbers.
[0105] In FIG. 3, the check valve 32 is a piston or flat slide
valve 80 with a longitudinally displaceable piston or slide 81
which, for actuation, is in an operative connection with the
actuator device 31, which is in the form of a control pressure
surface 105 on the check valve 32 that acts in the direction of the
open position 32b. For pressurization of the control pressure
surface 105 with the actuation pressure, the control pressure
surface 105 is connected with the branch line 60. The check valve
32 is pressurized toward the closed position 32a by the spring
device 38. Also provided on the check valve 32 is the additional
control pressure surface 100 that act in the direction of the
closed position 32a. The control pressure surface 100 is in
communication with the control pressure line 101 to hold the check
valve 32 in the closed position 32a during the startup of the
internal combustion engine 2 by the pressure of the hydraulic
accumulator 20 and, thus, the pressure in the suction line 8 and to
prevent the check valve 32 from being actuated into the open
position 32b before the end of the startup of the internal
combustion engine 2 by the charge pressure generated against the
force of the spring device 38.
[0106] When the internal combustion engine 2 is shut off and,
therefore, when the charge pump 15 is not being driven, and when
the control valve 25 is in the closed position 25a, the charge
pressure in the control pressure line 43 and the charge pressure in
the hydraulic line 50 connected to it drops, which acts on the
control pressure surface 105 so that the check valve 32 is pushed
by the spring device 38 into the closed position 32a. For startup
of the internal combustion engine 2, the control valve 25 is
actuated when the hydraulic accumulator 20 is charged with
hydraulic fluid into the open position 25b, so that when the check
valve 32 is in the closed position 32a, the internal combustion
engine 2 can be started by the power-unit 7 operated as a
motor.
[0107] For the duration of the startup process, the pressure of the
hydraulic accumulator 20 and the pressure in the suction line 8 are
present at the additional control pressure surface 100. As a
result, the check valve 32 is held in the closed position 32a and
the opening of the check valve 32 by the charge pressure present on
the control pressure surface 105 is prevented.
[0108] After the startup of the internal combustion engine 2, the
control valve 25 is actuated into the closed position 25a, so that
the pressure acting in the closing direction present at the
additional control pressure surface 100 from the hydraulic
accumulator 20 drops. The charge pressure generated by the driven
charge pump 15 is present via the branch line 60 at the control
pressure surface 105. As a result, the check valve 32 is actuated
into the open position 32b by the actuator device 31, which is a
control pressure surface 105.
[0109] In the exemplary embodiments illustrated in FIGS. 1 and 2,
the spring-side piston pressure chamber 36a of the positioning
piston 36 that acts in the closing direction 32a is depressurized
to the tank 9 via the depressurization line 39. The piston pressure
chamber 36b of the positioning piston 36, which acts in the opening
direction 32b, can be pressurized via the branch line 60 with the
actuation pressure (charge pressure), so that the operation of the
power-unit 7 as a motor makes it possible for the power-unit 7 to
act as a hydraulic starter for a start-stop function of the
shut-off internal combustion engine 2.
[0110] FIG. 4 illustrates a development of FIG. 1, in which
identical components are identified by the same reference numbers.
In FIG. 4, to control the pressurization of the actuator device 31,
a switching valve 90 is provided, by means of which, in a first
switched position 90a, the check valve 32 can be actuated as a
function of the actuation pressure into the open position 32b, and
by means of which, in a second switched position 90b, the check
valve 32 can be actuated into the closed position 32a. For this
purpose in FIG. 4, to control the pressurization of the piston
pressure chambers 36a, 36b of the positioning piston 36, there is a
switching valve 90, by means of which the piston pressure chamber
36b of the positioning piston 36, which in a first switched
position 90a acts in the opening direction 32b, is pressurized with
the actuator pressure and the spring-side piston pressure chamber
36a, which acts in the closed position 32b, is depressurized to the
tank 9. In a second switched position 90b, the spring-side piston
pressure chamber 36a of the positioning system 36, which acts in
the direction of the closing position 32a, is pressurized with the
actuation pressure and the piston pressure chamber 36b, which acts
in the direction of the open position 32b, is depressurized to the
tank 9.
[0111] For this purpose, the switching valve 90 is in communication
with the branch line 60 that carries the actuation pressure, the
depressurization line 39, and the two piston pressure chambers 36a,
36b of the positioning piston 36. The switching valve 90 is a
four-connection, two-position valve.
[0112] The switching valve 90 is an electrically actuated control
valve, preferably a switching valve, which can be actuated between
the switched positions 90a, 90b by the electrical actuator device
91, such as a switching magnet. For actuation, the switching valve
90 is operatively connected with the electronic control device
27.
[0113] If a separate housing 70 is provided for the check valve
device 30 illustrated in FIG. 1, the switching valve 90 is
preferably installed in the housing 70.
[0114] In the switched position 90a of the switching valve 90, the
result is the actuation of the check valve 32 described above and
illustrated in FIG. 1 that allows the power-unit 7 operating as a
motor to act as a hydraulic starter to provide a start-stop
function of the internal combustion engine 2.
[0115] The switched position 90b of the switching valve 90 makes
possible the reverse actuation of the check valve 32, so that by
operating the hydrostatic power-unit 7 as a motor when the internal
combustion engine 2 is running, an additional torque can be
delivered to the output shaft 6 of the internal combustion engine
2, thereby creating a booster drive. With the booster drive
provided by the hydrostatic power-unit 7, the internal combustion
engine 2 can be boosted during traction operation of the
vehicle.
[0116] For the booster drive, the switching valve 90 is actuated
into the switched position 90b, so that the charge pressure
generated by the driven charge pump when the internal combustion
engine 2 is running is present via the control pressure line 43,
the hydraulic line 50, and the branch line 60, in the spring-side
piston pressure chamber 36a of the positioning piston 36, which
acts in the direction of the closed position 32a of the check valve
32. Because in the switched position 90b of the switching valve 90
the piston pressure chamber 36b of the positioning piston 36, which
acts in the opening direction 32b, is depressurized to the tank 9,
when the internal combustion engine 2 is running, the check valve
32 is actuated into the closed position 32a to shut off the
connection of the suction line 8 in the flow direction to the tank
9. By actuating the control valve 25 into the flow position 25b,
the power-unit 7 can be operated as a motor with hydraulic fluid
under pressure from the hydraulic accumulator 20 to feed a torque
to the drivetrain to assist the running internal combustion engine
2.
[0117] In FIG. 4, in the closed position 32a of the check valve 32,
a connection is made possible between the suction side S and the
tank 9 in the direction of flow from the tank 9 to the suction side
S when the booster drive is in operation, for which purpose there
is a check valve 95 that opens toward the power-unit 7 in a bypass
line 96 of the suction line S which bypasses the check valve 32.
The check valve 95 makes it possible for the booster drive to suck
hydraulic fluid from the tank 9 by the power-unit 7 driven by the
running internal combustion engine 2 when the check valve 32 is in
the closed position 32b before the opening of the control valve 25
into the open position 25b for operation of the power-unit 7 as a
motor.
[0118] FIG. 5 illustrates a development of FIG. 3, with which the
switching valve 90 makes it possible for the hydrostatic power-unit
7 to function as a booster drive to assist the running internal
combustion engine 2.
[0119] The switching valve 90 is in communication with the branch
line 60 which carries the actuation pressure, the control pressure
line 101 connected to the connecting line 23, and the two control
pressure surfaces 100, 105. The switching valve 90 is a
four-connection, two-position valve and can be electrically
actuated by the electric actuator device 91.
[0120] In the first switched position 90a of the switching valve
90, the control pressure surface 105 of the check valve 32 is in
communication with the branch line 60 and is pressurized with the
actuation pressure. The additional control pressure surface 100 of
the check valve 32 is connected in the first switched position 90a
to the control pressure line 101 and is, thus, in communication
with the suction side S between the power-unit 7 and the check
valve 32. In the switched position 90a of the switching valve 90,
the result is the actuation of the check valve 32 described above
and illustrated in FIG. 3 for use of the power-unit 7, operating as
a motor, as a hydraulic starter in a start-stop function of the
internal combustion engine 2.
[0121] In the second switched position 90b of the switching valve
90, the control pressure surface 105 and the additional control
pressure surface 100 of the check valve 32 are connected to the
branch line 60 and are, thus, pressurized by the actuation
pressure. The control pressure line 101 in the second switched
position 90b of the switching valve 90 is shut off. As a result of
the actuation of the switching valve 90 into the second switched
position 90b, the check valve 32 is, therefore, actuated by the
spring device 38 into the closed position 32a.
[0122] For the booster drive, the switching valve 90 is actuated
into the switched position 90b, in which the check valve 32 is
actuated into the closed position 32a and the connection of the
suction line 8 in the direction of flow to the tank 9 is shut off.
As a result of the actuation of the switching valve 25 into the
open position 25b, the power-unit 7 can be driven with hydraulic
fluid under pressure from the hydraulic accumulator 20 and operated
as a motor to feed a torque into the drivetrain to assist the
running internal combustion engine 2.
[0123] FIG. 6 illustrates an additional development of FIG. 3 which
differs from FIG. 5 in the construction of the switching valve
90.
[0124] The switching valve 90 in FIG. 6 is a five-connection,
two-position valve which can be actuated electrically by the
electrical actuator device 91. The switching valve 90 is in
communication with the branch line 60 that carries the actuation
pressure, the control pressure line 101 connected to the connecting
line 23, the two control pressure surfaces 100, 105, and the
depressurization line 39 that leads to the tank 9.
[0125] In the first switched position 90a of the switching valve
90, the control pressure surface 105 of the check valve 32 is
connected with the branch line 60 and is pressurized with the
actuation pressure. The additional control pressure surface 100 of
the check valve 32 is connected in the first switched position to
the control pressure line 101 and is in communication with the
suction side S between the power-unit 7 and the check valve 32. The
depressurization line 39 is shut off. In the switched position 90a
of the switching valve 90, the result is the actuation of the check
valve 32 described above and illustrated in FIG. 3 for use of the
power-unit 7, operating as a motor, as a hydraulic starter in a
start-stop function of the internal combustion engine 2.
[0126] In the second switched position 90b of the switching valve
90, the control pressure surface 105 is in communication with the
depressurization line 39 and the additional control pressure
surface 100 is connected to the branch line 60 and is, thus,
pressurized by the actuation pressure. The control pressure line
101 is shut off. As a result of the actuation of the switching
valve 90 into the second switched position 90b, the check valve 32
is actuated by the spring device 38 and the charge pressure present
at the additional control pressure surface 100 into the closed
position 32a.
[0127] For the booster drive, the switching valve 90 is actuated
into the switched position 90b, in which the check valve 32 is
actuated into the closed position 32a and the connection of the
suction line 8 in the direction of flow to the tank 9 is shut off.
As a result of the actuation of the switched valve 25 into the open
position 25b, the power-unit 7 can be driven as a motor with
hydraulic fluid under pressure from the hydraulic accumulator 20 to
feed a torque into the drivetrain to assist the running internal
combustion engine 2.
[0128] In FIGS. 5 and 6, in the closed position 32a of the check
valve 32, a connection of the suction side S with the tank 9 in the
direction of flow from the tank 9 to the suction side S while the
booster drive is in operation becomes possible, for which purpose
in the closed position 32a, there is a check valve 95 that opens
toward the power-unit 7.
[0129] The invention has a series of advantages.
[0130] The check valve 32 of the invention, which can be actively
controlled by the actuator device 31 and can be actuated
hydrostatically by the actuation pressure, makes it possible for
the existing hydrostatic power-unit (which is used to supply the
working hydraulics 4 when operating as a pump) to also be operated
as a motor as a hydraulic starter for the internal combustion
engine 2 and/or as a booster drive to assist the running internal
combustion engine 2, such as during traction operation, without
creating additional hydraulic flow resistance in the suction side S
in pump operation, which would reduce the suction limit speed
during pump operation of the power-unit 7.
[0131] The actuator device 31 (positioning piston 36 or control
pressure surface 105) is pressurized in the direction of the open
position 32b of the check valve 32 by the pressure provided in the
form of the charge pressure of the charging pressure circuit 18
supplied by the charge pump 15 or by the actuation pressure in the
form of the pressure of the hydraulic accumulator 20 provided via
the pressure reducer valve 51, so that when the internal combustion
engine 2 is running, the check valve 32 is actuated into the open
position 32b. When the internal combustion engine 2 is shut off,
and the charge pressure consequently drops, and with the control
valve 25 in the closed position 25a, the check valve 32 is actuated
by the spring device 38 into the closed position 32a and is held in
the closed position 32a by the spring device 38. When the internal
combustion engine 2 is shut off, the check valve 32 is
automatically in the closed position 32a, so that for a start-stop
function by actuation of the control valve 25 into the open
position 25b, a hydrostatic start of the internal combustion engine
2 can be achieved immediately and directly by operating the
power-unit 7 as a motor without first having to actuate the check
valve 32 into the closed position 32a. The function of the check
valve 32 in a start-stop function and the use of the power-unit 7
as a hydraulic starter for the internal combustion engine 2 can be
achieved without additional control logic and additional control
valves for the actuation of the actuator device 31.
[0132] With the switching valve 90 illustrated in FIGS. 4-6, and
with a check valve device 30 illustrated in FIGS. 1-3, it becomes
possible in a simple manner to reverse the function of the
actuation of the check valve 32, so that when the internal
combustion engine 2 is running, the actuation of the check valve 32
into the closed position 32a by the actuation pressure in the form
of a constant charge pressure results in operation of the
power-unit 7 as a motor to deliver a torque to the output shaft 6
for a booster drive.
[0133] The invention is not restricted to the illustrated exemplary
embodiments.
[0134] The check valve 32 can be a piston slide valve with a
rotating piston or a ball cock with a rotating ball, whereby the
piston or the ball is in an operative connection with the actuator
device 31 and is actively rotated between a closed position and an
open position by the actuator device 31 (e.g., a positioning piston
36 or a control pressure surface 105).
[0135] The hydrostatic power-unit 7, as an alternative to the
realization in the form of an axial piston machine, can be a geared
machine, a radial piston machine, or any other common design, each
with a constant displacement volume or, alternatively, a
continuously variable displacement volume.
[0136] Nor is the invention restricted to the illustrated sequence
of the arrangement of the traction drive 3, the hydrostatic
power-unit 7, and the charge pump 15 on the output shaft 6 of the
internal combustion engine 2, the order and arrangement of which
can be varied and modified arbitrarily.
[0137] It will be readily appreciated by those skilled in the art
that modifications may be made to the invention without departing
from the concepts disclosed in the foregoing description.
Accordingly, the particular embodiments described in detail herein
are illustrative only and are not limiting to the scope of the
invention, which is to be given the full breadth of the appended
claims and any and all equivalents thereof.
* * * * *